Electric circuit breaker with removable trip unit having impact-releasable latch means



Nov. 15, 1966 c. F HOBSON, JR 3,286,210

ELECTRIC CIRCUIT BREAKER WITH REMOVABLE TRIP UNIT HAVING IMPACT-RELEASABLE LATCH MEANS Filed Jan. 25, 1965 INVEN TOR.

A TTORIVE V United States Patent 3,286,210 ELECTRIC CIRCUIT BREAKER WITH REMOVABLE TRIP UNIT HAVING IMPACT RELEASABLE LATCH MEANS Charles F. Hobson, J12, Southington, Conn., assignor to General Electric Company, a corporation of New York Filed Jan. 25, 1965, Ser. No. 427,725 4 Claims. (Cl. 335) The present invention relates to electric circuit breakers and particularly to electric circuit breakers of the multipole type having a main molded insulating enclosure or case containing a plurality of pairs of fixed and movable contacts including a releasable member for causing automatic opening of the contacts and including a separately enclosed current responsive mechanism or trip unit contained and supported within the main enclosure or case and adapted to cause release of the releasable member and automatic opening of the contacts upon the flow of overload currents of predetermined amplitude through the circuit breaker.

Such separately enclosed current responsive mechanisms of hip units are commonly adjusted and calibrated to cause automatic opening of the circuit breaker upon :the occurrence of particular predetermined cunent conditions beiore the .trip unit is mounted in the main case of the circuit breaker in engagement with the main current conducting portions and operating mechanism of the circuit breaker. Accordingly, the necessary adjustments for the trip unit are facilitated and trip units of different ratings may be exchange-ably mounted in a circuit breaker by the user as desired. Convenient replacement of damaged trip units by the user is afforded as well.

While such independently calibrated and preadjusted trip units are highly desirable, prior art devices of this ty e have had the disadvantage that in many instances such a precalibrated trip unit may operate somewhat differently than its indicated and desired preadjusted points of operation due to the influence and effect of forces such as friction, leverage, spring-bias, etc. of the main operating mechanism of the relatively movable main conducting contacts of the circuit breaker when the trip unit is mounted in the circuit breaker in engagement with such main operating mechanism. For example, the main contact operating mechanisms of such circuit breakers may vary slightly from one unit to another in the degree and amount of force tending to operate its releasable means. Additionally, there are unavoidable minor variations in the dimensions and characteristics of the cornponents of the main operating portion of the circuit breaker including the main insulating casing, the main contact operating mechanisms and the precise disposition in which such components are mounted relative .to each other, spring tension, etc.

Accordingly, it is a principal object of the present invention to provide an electric circuit breaker of the type referred to including a precalibratable trip unit, the adjustment of which is not altered by its engagement with the main contact operating mechanism of the circuit breaker when mounted in the main casing of such circuit breaker.

It is another object of the present invention to provide a trip unit of the type described which may be precali brated and adjusted independently of the circuit breaker with which it is to be used and may be readily mounted in or removed from such circuit breaker without disturbing such precalibration and adjustment.

Another object of the invention is .to provide an independently calibratable unit of the type described including a primary latch means and a secondary latch means to which the primary latch means is operatively respon- "ice sive and wherein the secondary latch means is actuated by the current responsive element of the trip unit and is configured, disposed and spring-biased to have an amount of free travel upon its release before acting upon the primary latch.

A further object of the present invention is to provide a trip unit of the type described in which the secondary latch means moves through an amount of such free travel for impact engagement with means ope-ratively respon sive to actuate and release the primary latch.

Yet another object of the present invention is to provide a trip unit having a spring biased secondary latch operatively related to a primary latch through a spring biased tripping assembly wherein the secondary latch has an amount of free .travel for impact engagement with the tripping assembly and the secondary latch bias is substantially greater than the tripping assembly bias.

In one form the invention comprises a .trip unit which is adapted for removable mounting in a multipole circuit breaker and comprises a casing enclosing the trip unit and having an aperture through which a portion of a tripping assembly extends in a spring-biased position to engage and restrain a releasable means of the main operating mechanism of the circuit breaker such as a primary latch which may be supported within the main insulating casing of the circuit breaker itself. A secondary latch is supported Within the trip unit and is spring biased for piv-otable movement. The secondary latch being positioned biased and configured for impact engagement with the tripping assembly during biased pivotable movement and the secondary latch bias being substantially greater than the tripping assembly bias so that the tripping assembly is readily-and positively actuated upon engagement by the secondary latch. Ourrent responsive means within the trip unit is positioned to normally restrain the secondary latch and adapted to be actuated by the flow of predetermined overload current to release the secondary latch for impact engagement with the tripping assembly in the manner described.

The trip unit of the present invention is preferably mounted in a multipole electric circuit breaker which includes a main insulating casing and at least two pairs of relatively movable contacts supported in the main casing and has a member releasable to cause automatic opening of the cont-acts. The releasable member may be arranged to be releasably engaged by a primary latch disposed and supported within the main insulating casing of the circuit breaker and in turn be restrainingly engaged by the tripping assembly of the trip unit which extends through an aperture in the trip unit casing. The common trip bar carried by the trip unit extends across all poles of the multipole circuit breaker so as to cause automatic opening of the main contacts of the circuit breaker upon actuation of any one of the several current responsive means which may be carried by the trip unit for each of the poles of the circuit breaker.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a side elevational view of an electric circuit breaker incorporating the invention, a portion of the side wall of the main casing of the circuit breaker being broken away;

FIGURE 2 is a side elevational view of the latching mechanism of the present invention illustrating its operative relationship to elements of the main contact operating mechanism of the circuit breaker of FIG- URE 1;

FIGURE 3 is a side elevational view illustrating the manner of release of the latching mechanism of FIGURE 2 and,

FIGURE 4 is a perspective view of the latching mechanism of the trip unit of the present invention.

Referring now to FIGURE 1, the invention is shown as being incorporated in a circuit breaker which comprises a main molded insulating casing housing a plurality of incoming and outgoing terminal means 11 and 12, respectively, only one of each being shown. Several pairs of relatively movable contacts such as those shown at 13 and 14 and 15 and 16 are connected between each incoming terminal as shown at 11 and its corresponding outgoing terminal as shown at 12. Typically, a circuit breaker of the type illustrated in FIGURE 1 may have a current carrying capacity rated in the order of 600 to 1200 amperes and is provided with a pair of relatively movable arcing contacts 13 and 14 and several pairs of main current carrying contacts only one of which is shown at 15 and 16. The stationary contacts 14 and 16 are fixedly supported on a conductor 17 while the movable contacts 13 and 15 are supported on a movable contact arm 18 pivotally supported at its ends on suitable bearing means (not shown) which are in turn mounted in the base of the insulating casing 10. A contact cross arm 19 extends across the plurality of poles of the multipole circuit breaker and is rigidly afiixed to a number of contact arms similar to that shown at 18. The movable contact arm 18 is connected through suitable conductors including the flexible stranded conductor 20 to a terminal strap 21 of the trip unit 22. Each terminal strap such as that shown at 21 of the trip unit is connectable electrically through the trip unit to a corresponding outgoing terminal strap as shown at 23. For the purpose of operating the contact arm 18 and the plurality of relatively movable contacts which its supports thereon, an operating mechanism is provided which comprises a reciprocally operable handle 24 extending through an aperture in the insulating casing 10 which is pivotally supported and operatively engaged with an overcenter spring mechanism shown generally at 25 including a releasable member 26. The releasable member 26 has a latch portion 26a which is configured to be engageable and releasably held in latched position by a primary latch 27. The reciprocally operable external handle 24 may be positioned in the of position (to the left in FIGURE 1, as shown by the dash line outline) causing the several pairs of contacts on the contact arm 18 to disengage, thereby interrupting the fiow of current through the circuit breaker. Alternatively, current responsive means within the trip unit 22 will, upon the flow of overload currents of predetermined amplitude, act upon the primary latch 27 causing it to release the releasable member 26 from its latched position and actuating the main operating mechanism 25 of the circuit breaker to disengage the several pairs of relatively movable contacts such as those shown at 13 and 14 and at 15 and 16. The operation of the latching mechanism of the present invention will be more fully understood from FIGURES 2, 3 and 4 wherein like members bear the same numerical designations as in FIG- URE 1.

Referring now to FIGURE 2, there is Shown the releasable member 26 of the main operating mechanism of the circuit breaker which has its latch portion 26a in engagement with a primary latch 27. The primary also operatively engaged at its lower end with a pair of toggle links of the tripping assembly as shown at 34 and 35. The toggle links 34 and 35 are connected to a common pin 36 and the toggle link 35 is pivotally supported by a suitable pin means 37 so that the toggle linkage comprising the members 34 and 35 are collapsible about their common pin 36.

A suitable spring means 38 biases the link 30 toward counterclockwise movement about its pivotal support 31 and is also engaged with the toggle link 34, urging that member in counterclockwise movement about the tripping member 29 so that the toggle linkage comprising links 35 and 34 is urged to collapse downwardly about its common pin 36. Thus the toggle links 34 and 35 are movable between straightened and collapsed positions and their straightened set position may be adjustably determined by an adjustable threaded means 39 supported in fixed relation to the toggle link 35 and its extension 35b. A secondary latch 40 is supported pivotally by the pin 37 and independently of the toggle link 35. The secondary latch 40 has a latch portion 40a which is positioned to be engageable with the trip bar 41. The trip bar 41 is pivotable about a suitable pivot support 42 and is operably connected to a current responsive means which may be either thermally or magnetically sensitive or both, to release the secondary latch 40 and initiate the actuation which results in the automatic disengagement of the contacts of the main operating mechanism of the circuit breaker in a manner which will be more fully described hereinafter. The link 40 is connected at its lower end through a suitable pin means 43 to a toggle 44 which in turn is connected to a member 45 which performs in the manner of a toggle link through the common pin connection 46. Member 45 is supported on a boss 47 extending from the casing 33 of the trip unit 22 and is spring biased by the spring 48 to be urged in a clockwise direction thereby urging the secondary latch member 40 in a counterclockwise direction under such spring bias. It should be noted that the toggle link 35 of the tripping assembly has an extending portion 35a and the secondary latch 40 has a pin 40b which extends therefrom and is positioned to be engageable with the extension 35a of the toggle link 35, after some counterclockwise movement of secondary latch 40 upon its release from latched engagement with the trip bar 41, due to the bias action of spring 48 acting through member 45 and toggle link 44.

As was previously mentioned, the illustration of FIG- URE 2 shows the latching mechanism of the trip unit of the present invention in its latched condition and its operation to actuate and disengage the main contact of the circuit breaker upon the flow of overload currents are predetermined amplitude therethrough is as follows. Current responsive means in the form of thermally or magnetically sensitive devices urge the trip bar 41 in a counterclockwise direction about its pivot 42; the latch portion 40a of the secondary latch 40 which is engaged with the trip bar 41, is urged to the left as illustrated in FIGURE 2, the secondary latch 40 tending to rotate in a counterclockwise direction about its pivot point 37. An important aspect of a preferred embodiment of the present invention as illustrated in FIGURE 2, is the fact that the pin 4% which extends from secondary latch 40 to be engageable with the extension 35a on toggle link 35 is spaced away from engagement with the extension 35a in the normal, latched, condition of the parts as shown in FIG. 2. This aspect of the latching mechanism assures a definite amount of free travel between the secondary latch 40 and the toggle linkage of the tripping assembly before the two come into engagement. Upon movement of the trip bar 41 in a counterclockwise direction, the latch portion 40a of the secondary latch 40 becomes disengaged from retention by the trip bar and responds to the bias of spring 48 which urges the member 45 in clockwise movement drawing the links 44 and 40 with it as shown in FIGURE 3 so that the extending pin 4011 comes into engagement with the extending portion 35a of the toggle link 35, upsetting and collapsing the toggle linkage 34 and 35 of the tripping assembly. The link member 30 consequently has its lower end moved inwardly, drawing the tripping member 29 away from engagement with the primary latch 27. The primary latch 27 bias is readily overcome by the much stronger bias of the releasable member 26 causing unlatching of the releasable member 26 of the main operating mechanism of the circuit breaker which operates through an appropriate overcenter spring arrangement 25 as shown in FIGURE 1 to disengage the main current carrying contacts .and the arcing contacts of the circuit breaker in all of its plurality of poles by common action through the cross arm 19. At the end of the travel of the several pairs of contact arms in the multipole circuit breaker the cross arm 19 comes into contact with the face of member 45 and its momentum resets the spring 48 and its associated linkage for latched engagement and another cycle of operation such as that described. Certain aspects of the mechanism disclosed herein, particularly relating to the action of the contact cross-arm in resetting the latch mechanism are disclosed and claimed in co-pending application Serial Number 427,717, filed January 25, 1965 and assigned to the same assignee as the present invention. The releasable member 26 is reset in latched engagement with the primary latch 27 by means of the externally extending reciprocally operable handle 24.

FIGURE 4 illustrates in perspective view the members of the latching mechanism of the trip unit of the present invention and like members bear the same numerical designations as in FIGURES 1, 2 and 3. As shown in FIGURE 4, the trip bar 41 is a common member extending to all poles of the multipole circuit breaker, its extension to other parts of the circuit breaker being indicated by the broken lines of member 41. Accordingly, the trip bar 41 is adapted to respond to the action of current responsive means in any of the plurality of poles of the multipole circuit breaker. Upon such actuation by current responsive means, the trip bar 41 is rotated in a counterclockwise direction about its pivot means 42. It is to be noted that the secondary latch 40 and the toggle link 35 are independently supported on the pivot pin 37, so as to be movable independently of each other except for such engagement as is effected by engagement of the pin extension 40b with the toggle link extension 3511. The outer end of toggle link 35 is adjustable stopped in the position of FIGURE 2 by the threaded adjustable means 39 as will be recalled from the description of FIGURE 2. As the trip bar 41 continues to move in a counterclockwise direction, it passes through a point where the extending portion 41a of the trip bar 41 becomes disengaged from the latch portion 40a of the latch 40 allowing the spring bias of spring 48 to move member 45, toggle link 44, and the secondary latch 40 under the resilient force of spring 48. The pin 40b being displaced from the extension 35a of toggle link 35 as was previously described, begins to move in free travel under the spring bias of spring 48 rapidly toward the extension 35a of toggle link 35. The extending pin 40b strikes the extending portion 35a of toggle link 35 with an impact engagement effecting a kickoff action which collapses the toggle linkage of the tripping assembly comprising links 34 and 35 upwardly about pivotal point 36 against the spring bias of spring 38. It should be especially noted that the spring bias of spring 48 is substantially greater than that of spring 38 so that the previously mentioned kick-01f action upon impact engagement of the extending pin 40b with the extension 35a is a positive action in which the bias of spring 38 is easily and readily overcome, thus disengaging the tripping member 29 from restraining engagement with the primary latch 27 allowing the primary latch 27 to be rotated in a counterclockwise direction releasing the releasable member 26 from latched engagement therewith, and actuating the main operating mechanism of the trip breaker to disengage the current carrying contacts.

The highly desirable results afforded by the present in vention are that the forces associated with the main operating mechanism of the circuit breaker such as might result from friction, leverage, spring bias and the like are not reflected into the trip unit of the present invention to effect its preestablished calibration and predetermined operative points. This is effected by reason of the trip unit itself embodying the only spring bias, frictional, and lever actions which are directly related to the action of the trip bar and its engageable secondary latch. Moreover, the variations in sizes of components spring strength, and the like of the main operating mechanism are isolated from the calibration of the trip unit. For instance, referring to FIGURES 2, 3 and 4, it may be seen that the trip bar 41 will consistently respond to the conditions reflected by its calibration as determined in connection with the spring bias of spring 48, the frictional forces attendant at the latching surfaces of 40a and 41a and the frictional forces which may be present in the several connecting pins and pivot pins. The remainder of the latching mechanism operates independently of the release of the secondary latch 40. It is only after the release of secondary latch in calibrated response, and the subsequent free travel of secondary latch 40, that operative engagement of the remainder of the mechanism follows from the impact engagement of the pin 4% with an extending portion of the toggle link 3511. It is only at this point that forces other than the spring bias of spring 48 may be reflected into the latching mechanism but since the secondary latch 40 has already been released, such forces do not affect its point of release nor its calibrated actuation.

Moreover, the fact that the present invention contemplates that spring 48 provides a substantially greater spring bias than spring 38, insures a positive upset action of the toggle links 35 and 34 about their common point 36 to disengage the tripping member from the primary latch and allow the spring biased actuation of the releasable member 26 of the main operating mechanism of the circuit breaker, disengaging the main current carrying contacts thereof. It will be evident to those skilled in the art that the frictional forces which may be present between the releasable member 26 and the primary latch 27, between the primary latch 27 and the tripping member 29, and the several connecting points such as 36, 31 and the bearing support for tripping member 29, as well as the pivotal points 28 and 37, cannot be reflected into the calibrated operation of the trip bar 41 as it relates to the secondary latch 40. Therefore, the present invention affords a trip unit which may be mounted in a multipole circuit breaker after having been calibrated independently without disturbance or distortion of its predetermined calibration and operating points. Additionally, within the concept of the present invention, trip units of different calibration and different predetermined operating points may be readily precalibrated at the factory, forwarded to a user for substitution in a multipole circuit breaker with assured operation within its predetermined and specified performance. The concept of the present invention is such that it may be embodied in a number of different forms such as, for instance, the secondarylatch 40 may have an extending portion configured to engage the toggle link 34 or the connecting pin 36 instead of the extending pin 40b which engages the extending portion 35a and the toggle link 35. The resulting actuation will be the same and the isolation of forces inherent in the main operating portion of the circuit breaker are isolated from the critical precalibrated portions of the trip mechanism in the same manner as the embodiment illustrated in FIGURES 2, 3 and 4. Still other configurations to carry out the concept and the spirit of the present invention can be executed within its scope as will be apparent to those skilled in the art.

While only one embodiment of the present invention has been illustrated and described, it will be appreciated that many modifications thereof may be made, and it is 7 intended, therefore, that the appended claims shall cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A multipole electric circuit breaker comprising: a main insulating casing; at least two pairs of relatively movable contacts supported in said casing; a member releasable to cause automatic opening of said contacts; a primary latch disposed and arranged to releasably engage said releasable member; a separately enclosed trip unit removably mounted in said main insulating casing; a tripping assembly supported on said trip unit to engage said primary latch and biased to restrain said primary latch in engagement with said releasable member; a secondary latch supported on said trip unit and biased to move into engagement with said tripping assembly for releasably disengaging said tripping assembly from said primary latch; a common trip bar carried by said trip unit and extending across all poles of said multipole circuit breaker; at least one current responsive means carried by said trip unit for each of said poles and arranged and disposed to engage said common trip bar, and means carried by said common trip bar restraining said secondary latch .from engagement with said tripping assembly, said restraining means being releasable upon a predetermined amount of movement of said common trip bar by said current responsive means.

2. A multipole electric circuit breaker comprising: a main insulating casing; at least two pairs of relatively movable contacts supported in said casing; a member releasable to cause automatic opening of said contacts; a primary latch disposed and arranged to releasably engage said releasable member; a separately enclosed trip unit removably mounted in said main insulating casing; a tripping assembly supported on said trip unit for biased engagement with said primary latch, restraining said primary latch in engagement with said releasable member; a secondary latch supported on said trip unit and biased to move into engagement with said tripping assembly for releasably disengaging said tripping assembly from said restraining engagement with said primary latch, said secondary latch bias being substantially greater than said tripping assembly bias; a common trip bar carried by said trip unit and extending across all poles of said multipole circuit breaker; at least one current responsive means carried by said trip unit for each of said poles and arranged and disposed to engage said common trip bar, and means carried by said common trip bar restraining said secondary latch from engagement with said tripping assembly, said restraining means being releasable upon a predetermined amount of movement of said trip bar by said current responsive means.

3. A multipole electric circuit breaker comprising a main insulating casing; at least two pairs of relatively movable contacts supported in said casing; a member releasable to cause automatic opening of said contacts; a primary latch disposed and arranged to releasably engage said releasable member; a separately enclosed trip unit removably mounted in said main insulating casing;

a tripping assembly supported on said trip unit for biased engagement with said primary latch, restraining said primary latch in engagement with said releasable member; a secondary latch supported on said trip unit and biased for pivotal movement, said secondary latch having an extending portion positioned for impact engagement upon said biased pivotal movement for releasably disengaging said tripping assembly from said primary latch; a common trip bar carried by said trip unit and extending across all poles of said multipole circuit breaker; at least one current responsive means carried by said trip unit for each of said poles and arranged and disposed to engage said common trip bar, and means carried by said common trip bar restraining said secondary latch from engagement with said tripping assembly, said restraining means. being releasable upon a predetermined amount of movement of said common trip bar by said current responsive means.

4. A multipole electric circuit breaker comprising: a main insulating casing; at least two pairs of relatively movable contacts supported in said casing; a member releasable to cause automatic opening of said contacts; a primary latch disposed and arranged to releasably engage said releasable member; a separately enclosed trip unit removably mounted in said main insulating casing; a tripping assembly mounted on said trip unit and including a toggle linkage biased toward straightened position for supporting a tripping member to restrain and maintain said primary latch in latched engagement with said releasable member; a secondary latch supported on said trip unit and biased to move into engagement with said tripping assembly for releasably disengaging said tripping assembly from said restraining engagement with said primary latch, said secondary latch bias being substantially greater than said tripping assembly bias; a common trip bar carried by said trip unit and extending across all poles of said multipole circuit breaker; at least one current responsive means carried by said trip unit for each of said poles and arranged and disposed to engage said common trip bar, and means carried by said common trip bar restraining said secondary latch from engagement with said tripping assembly, said restraining means being releasable upon a predetermined amount of movement of said common trip bar by said current responsive means.

References Cited by the Examiner UNITED STATES PATENTS References Cited by the Applicant UNITED STATES PATENTS 2,047,828 7/1936 Lappin. 2,778,902 1/1957 Visos.

BERNARD A. GILHEANY, Primary Examiner.

H. B, GILSON, Assistant Examiner. 

1. A MULTIPOLE ELECTRIC CIRCUIT BREAKER COMPRISING: A MAIN INSULATING CASING; AT LEAST TWO PAIRS OF RELATIVELY MOVABLE CONTACTS SUPPORTED IN SAID CASING; A MEMBER RELEASABLE TO CAUSE AUTOMATIC OPENING OF SAID CONTACTS; A PRIMARY LATCH DISPOSED AND ARRANGED TO RELEASABLY ENGAGE SAID RELEASABLE MEMBER; A SEPARATELY ENCLOSED TRIP UNIT REMOVABLY MOUNTED IN SAID MAIN INSULATING CASING; A TRIPPING ASSEMBLY SUPPORTED ON SAID TRIP UNIT TO ENGAGE SAID PRIMARY LATCH AND BIASED TO RESTRAIN SAID PRIMARY LATCH IN ENGAGEMENT WITH SAID RELEASABLE MEMBER; A SECONDARY LATCH SUPPORTED ON SAID TRIP UNIT AND BIASED TO MOVE INTO ENGAGEMENT WITH SAID TRIPPING ASSEMBLY FOR RELEASABLY DISENGAGING SAID TRIPPING ASSEMBLY FROM SAID PRIMARY LATCH; A COMMON TRIP BAR CARRIED BY SAID TRIP UNIT AND EXTENDING ACROSS ALL POLES OF SAID MULTIPOLE CIRCUIT BREAKER; AT LEAST ONE CURRENT RESPONSIVE MEANS CARRIED BY SAID TRIP UNIT FOR EACH OF SAID POLES AND ARRANGED AND DISPOSED TO ENGAGE SAID COMMON TRIP BAR, AND MEANS CARRIED BY SAID COMMON TRIP BAR RESTRAINING SAID SECONDARY LATCH FROM ENGAGEMENT WITH SAID TRIPPING ASSEMBLY, SAID RESTRAINING MEANS BEING RELEASABLE UPON A PREDETERMINED AMOUNT OF MOVEMENT OF SAID COMMON TRIP BAR BY SAID CURRENT RESPONSIVE MEANS. 